Figure 1.

Various forms of acute myocarditis and inflammatory cardiomyopathy demonstrated by histological and immunohistochemical staining using endomyocardial biopsies. (A) Inflammatory cardiomyopathies are characterized by diffuse, low-grade infiltration of CD3⁺ T cells and MAC-1⁺ macrophages, as well as HLA-DR activation. (B) Lymphocytic myocarditis is also characterized by diffuse infiltration of mainly lymphocytic cells and HLA-DR activation, in combination with myocytolysis. (C) In eosinophilic myocarditis, the main inflammatory cells are eosinophilic granulocytes and macrophages. (D) Giant cell myocarditis is characterized by patchy infiltration of mononuclear and lymphocytic cells, HLA-DR activation, myocytolysis, and eosinophils in the presence of giant cells (arrows). (E) Cardiac sarcoidosis is also characterized by evidence of granulomas (*) and patchy immune cell infiltrates plus HLA-DR activation, but without myocytolysis. Magnification: 200× or 400×, scale bar: 50 µm.